EVM-900-DT Ver la hoja de datos (PDF) - Unspecified

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EVM-900-DT

HumDT™ Series RF Transceiver Module

Unspecified 

Power Supply Requirements

The module does not have an internal

voltage regulator, therefore it requires a clean,

Vcc TO

MODULE

well-regulated power source. The power supply

10Ω

noise should be less than 20mV. Power supply Vcc IN

noise can significantly affect the module’s

10µF

performance, so providing a clean power supply

for the module should be a high priority during

design.

Figure 59: Supply Filter

A 10Ω resistor in series with the supply followed by a 10μF tantalum

capacitor from Vcc to ground helps in cases where the quality of supply

power is poor (Figure 59). This filter should be placed close to the module’s

supply lines. These values may need to be adjusted depending on the

noise present on the supply line.

Antenna Considerations

The choice of antennas is a

critical and often overlooked

design consideration. The range,

performance and legality of an RF

link are critically dependent upon the

antenna. While adequate antenna

performance can often be obtained

by trial and error methods, antenna

design and matching is a complex Figure 60: Linx Antennas

task. Professionally designed antennas such as those from Linx (Figure

60) help ensure maximum performance and FCC and other regulatory

compliance.

Linx transmitter modules typically have an output power that is higher

than the legal limits. This allows the designer to use an inefficient antenna

such as a loop trace or helical to meet size, cost or cosmetic requirements

and still achieve full legal output power for maximum range. If an efficient

antenna is used, then some attenuation of the output power will likely be

needed.

It is usually best to utilize a basic quarter-wave whip until your prototype

product is operating satisfactorily. Other antennas can then be evaluated

based on the cost, size and cosmetic requirements of the product.

Additional details are in Application Note AN-00500.

– 54 –

Helpful Application Notes from Linx

It is not the intention of this manual to address in depth many of the issues

that should be considered to ensure that the modules function correctly

and deliver the maximum possible performance. We recommend reading

the application notes listed in Figure 61 which address in depth key areas

of RF design and application of Linx products. These applications notes

are available online at www.linxtechnologies.com or by contacting the Linx

literature department.

Helpful Application Note Titles

Note Number Note Title

AN-00100

RF 101: Information for the RF Challenged

AN-00126

Considerations for Operation Within the 902–928MHz Band

AN-00130

Modulation Techniques for Low-Cost RF Data Links

AN-00140

The FCC Road: Part 15 from Concept to Approval

AN-00500

Antennas: Design, Application, Performance

AN-00501

Understanding Antenna Specifications and Operation

Figure 61: Helpful Application Note Titles

– 55 –

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